It is well known that vinyl resins may be plasticized or changed from the hard, horny and stiff state to a soft, plastic workable condition by the addition thereto, at elevated temperatures, of certain plasticizers, such as dioctyl phthalate, and the like. These vinyl polymers or resins are referred to as dispersion resins or paste resins and are usually made by means of an emulsion polymerization technique.
When the vinyl resin is mixed or blended with a plasticizer, it is referred to as a "plastisol". By virtue of the flowability of the plastisol it can be processed into various useful products. The plastisols can be used in making molded products, coatings, and the like. Accordingly, the dispersion resin must be capable of being mixed with a plasticizer easily and uniformly to form low viscosity plastisols which are stable, containing particles of uniform and proper size, and capable of producing films, and like products, of good clarity.
It is known in the art to produce dispersion or paste resins by the emulsion polymerization process using an emulsifier system comprising the ammonium salt of a high fatty acid and at least one long straight chain alcohol.
These dispersion resins have improved flow properties and heat stability and films produced therefrom have excellent clarity and improved water resistance. However, the plastisol bloom properties of such resins leave a lot to be desired. Bloom can best be described as a hazy material which comes to the surface of the film cast from plastisols containing said resins. It is caused by the fact that the emulsifier or emulsifier system used in making the dispersion resin is not completely compatible with the other ingredients of the plastisol, such as the plasticizers, for example. While the bloom or precipitate can be wiped off the surface of the film, the bloom reoccurs with age thus making the film unattractive when the bloom is severe. A certain amount of bloom occurs with all plastisols but there is a continual effort being made in the art to find an emulsifier or emulsifier system for use in emulsion polymerization of vinyl monomers which entirely eliminates bloom or reduces the same to a minimum.
Another problem in the commercial production of homopolymers and copolymers of vinyl and vinylidene halides is the formation of undesirable polymer buildup on the inner surfaces of the polymerization reactor or vessel. This buildup interferes with heat transfer and decreases productivity and adversely affects polymer quality. It must be removed at considerable reduction in production time and if not removed, more polymer buildup occurs rapidly on that already present resulting in a hard, insoluble crust. Accordingly, it is not only desirable to have an emulsion polymerization process in which vinyl resins are produced that have the properties of eliminating bloom in finished articles made therefrom, or at least reducing the bloom to a minimum, but also in which polymer buildup on the inner surfaces of the reactor is substantially reduced or eliminated.